docs: def render_pdf_file_to_image_files_pdftoppm_pgm(pdf_file_name, root_output_file_path,
                                             res_x=150, res_y=150):
      """Same as renderPdfFileToImageFile_pdftoppm_ppm but with -gray option for pgm."""
  
      comm_output = render_pdf_file_to_image_files_pdftoppm_ppm(pdf_file_name,
                                          root_output_file_path, res_x, res_y, ["-gray"])
      return comm_output